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linux/net/ipv4/ip_options.c
David S. Miller 0374d9ceb0 ipv4: Kill spurious write to iph->daddr in ip_forward_options(). 
This code block executes when opt->srr_is_hit is set.  It will be
set only by ip_options_rcv_srr().

ip_options_rcv_srr() walks until it hits a matching nexthop in the SRR
option addresses, and when it matches one 1) looks up the route for
that nexthop and 2) on route lookup success it writes that nexthop
value into iph->daddr.

ip_forward_options() runs later, and again walks the SRR option
addresses looking for the option matching the destination of the route
stored in skb_rtable().  This route will be the same exact one looked
up for the nexthop by ip_options_rcv_srr().

Therefore "rt->rt_dst == iph->daddr" must be true.

All it really needs to do is record the route's source address in the
matching SRR option adddress.  It need not write iph->daddr again,
since that has already been done by ip_options_rcv_srr() as detailed
above.

Signed-off-by: David S. Miller <davem@davemloft.net>
2011-05-13 17:15:50 -04:00

647 lines
15 KiB
C
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/*
* INET An implementation of the TCP/IP protocol suite for the LINUX
* operating system. INET is implemented using the BSD Socket
* interface as the means of communication with the user level.
*
* The options processing module for ip.c
*
* Authors: A.N.Kuznetsov
*
*/
#include <linux/capability.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/types.h>
#include <asm/uaccess.h>
#include <linux/skbuff.h>
#include <linux/ip.h>
#include <linux/icmp.h>
#include <linux/netdevice.h>
#include <linux/rtnetlink.h>
#include <net/sock.h>
#include <net/ip.h>
#include <net/icmp.h>
#include <net/route.h>
#include <net/cipso_ipv4.h>
/*
* Write options to IP header, record destination address to
* source route option, address of outgoing interface
* (we should already know it, so that this function is allowed be
* called only after routing decision) and timestamp,
* if we originate this datagram.
*
* daddr is real destination address, next hop is recorded in IP header.
* saddr is address of outgoing interface.
*/
void ip_options_build(struct sk_buff *skb, struct ip_options *opt,
__be32 daddr, struct rtable *rt, int is_frag)
{
unsigned char *iph = skb_network_header(skb);
memcpy(&(IPCB(skb)->opt), opt, sizeof(struct ip_options));
memcpy(iph+sizeof(struct iphdr), opt->__data, opt->optlen);
opt = &(IPCB(skb)->opt);
if (opt->srr)
memcpy(iph+opt->srr+iph[opt->srr+1]-4, &daddr, 4);
if (!is_frag) {
if (opt->rr_needaddr)
ip_rt_get_source(iph+opt->rr+iph[opt->rr+2]-5, rt);
if (opt->ts_needaddr)
ip_rt_get_source(iph+opt->ts+iph[opt->ts+2]-9, rt);
if (opt->ts_needtime) {
struct timespec tv;
__be32 midtime;
getnstimeofday(&tv);
midtime = htonl((tv.tv_sec % 86400) * MSEC_PER_SEC + tv.tv_nsec / NSEC_PER_MSEC);
memcpy(iph+opt->ts+iph[opt->ts+2]-5, &midtime, 4);
}
return;
}
if (opt->rr) {
memset(iph+opt->rr, IPOPT_NOP, iph[opt->rr+1]);
opt->rr = 0;
opt->rr_needaddr = 0;
}
if (opt->ts) {
memset(iph+opt->ts, IPOPT_NOP, iph[opt->ts+1]);
opt->ts = 0;
opt->ts_needaddr = opt->ts_needtime = 0;
}
}
/*
* Provided (sopt, skb) points to received options,
* build in dopt compiled option set appropriate for answering.
* i.e. invert SRR option, copy anothers,
* and grab room in RR/TS options.
*
* NOTE: dopt cannot point to skb.
*/
int ip_options_echo(struct ip_options *dopt, struct sk_buff *skb)
{
const struct ip_options *sopt;
unsigned char *sptr, *dptr;
int soffset, doffset;
int optlen;
__be32 daddr;
memset(dopt, 0, sizeof(struct ip_options));
sopt = &(IPCB(skb)->opt);
if (sopt->optlen == 0)
return 0;
sptr = skb_network_header(skb);
dptr = dopt->__data;
daddr = skb_rtable(skb)->rt_spec_dst;
if (sopt->rr) {
optlen = sptr[sopt->rr+1];
soffset = sptr[sopt->rr+2];
dopt->rr = dopt->optlen + sizeof(struct iphdr);
memcpy(dptr, sptr+sopt->rr, optlen);
if (sopt->rr_needaddr && soffset <= optlen) {
if (soffset + 3 > optlen)
return -EINVAL;
dptr[2] = soffset + 4;
dopt->rr_needaddr = 1;
}
dptr += optlen;
dopt->optlen += optlen;
}
if (sopt->ts) {
optlen = sptr[sopt->ts+1];
soffset = sptr[sopt->ts+2];
dopt->ts = dopt->optlen + sizeof(struct iphdr);
memcpy(dptr, sptr+sopt->ts, optlen);
if (soffset <= optlen) {
if (sopt->ts_needaddr) {
if (soffset + 3 > optlen)
return -EINVAL;
dopt->ts_needaddr = 1;
soffset += 4;
}
if (sopt->ts_needtime) {
if (soffset + 3 > optlen)
return -EINVAL;
if ((dptr[3]&0xF) != IPOPT_TS_PRESPEC) {
dopt->ts_needtime = 1;
soffset += 4;
} else {
dopt->ts_needtime = 0;
if (soffset + 7 <= optlen) {
__be32 addr;
memcpy(&addr, dptr+soffset-1, 4);
if (inet_addr_type(dev_net(skb_dst(skb)->dev), addr) != RTN_UNICAST) {
dopt->ts_needtime = 1;
soffset += 8;
}
}
}
}
dptr[2] = soffset;
}
dptr += optlen;
dopt->optlen += optlen;
}
if (sopt->srr) {
unsigned char *start = sptr+sopt->srr;
__be32 faddr;
optlen = start[1];
soffset = start[2];
doffset = 0;
if (soffset > optlen)
soffset = optlen + 1;
soffset -= 4;
if (soffset > 3) {
memcpy(&faddr, &start[soffset-1], 4);
for (soffset-=4, doffset=4; soffset > 3; soffset-=4, doffset+=4)
memcpy(&dptr[doffset-1], &start[soffset-1], 4);
/*
* RFC1812 requires to fix illegal source routes.
*/
if (memcmp(&ip_hdr(skb)->saddr,
&start[soffset + 3], 4) == 0)
doffset -= 4;
}
if (doffset > 3) {
memcpy(&start[doffset-1], &daddr, 4);
dopt->faddr = faddr;
dptr[0] = start[0];
dptr[1] = doffset+3;
dptr[2] = 4;
dptr += doffset+3;
dopt->srr = dopt->optlen + sizeof(struct iphdr);
dopt->optlen += doffset+3;
dopt->is_strictroute = sopt->is_strictroute;
}
}
if (sopt->cipso) {
optlen = sptr[sopt->cipso+1];
dopt->cipso = dopt->optlen+sizeof(struct iphdr);
memcpy(dptr, sptr+sopt->cipso, optlen);
dptr += optlen;
dopt->optlen += optlen;
}
while (dopt->optlen & 3) {
*dptr++ = IPOPT_END;
dopt->optlen++;
}
return 0;
}
/*
* Options "fragmenting", just fill options not
* allowed in fragments with NOOPs.
* Simple and stupid 8), but the most efficient way.
*/
void ip_options_fragment(struct sk_buff * skb)
{
unsigned char *optptr = skb_network_header(skb) + sizeof(struct iphdr);
struct ip_options * opt = &(IPCB(skb)->opt);
int l = opt->optlen;
int optlen;
while (l > 0) {
switch (*optptr) {
case IPOPT_END:
return;
case IPOPT_NOOP:
l--;
optptr++;
continue;
}
optlen = optptr[1];
if (optlen<2 || optlen>l)
return;
if (!IPOPT_COPIED(*optptr))
memset(optptr, IPOPT_NOOP, optlen);
l -= optlen;
optptr += optlen;
}
opt->ts = 0;
opt->rr = 0;
opt->rr_needaddr = 0;
opt->ts_needaddr = 0;
opt->ts_needtime = 0;
}
/*
* Verify options and fill pointers in struct options.
* Caller should clear *opt, and set opt->data.
* If opt == NULL, then skb->data should point to IP header.
*/
int ip_options_compile(struct net *net,
struct ip_options * opt, struct sk_buff * skb)
{
int l;
unsigned char * iph;
unsigned char * optptr;
int optlen;
unsigned char * pp_ptr = NULL;
struct rtable *rt = NULL;
if (skb != NULL) {
rt = skb_rtable(skb);
optptr = (unsigned char *)&(ip_hdr(skb)[1]);
} else
optptr = opt->__data;
iph = optptr - sizeof(struct iphdr);
for (l = opt->optlen; l > 0; ) {
switch (*optptr) {
case IPOPT_END:
for (optptr++, l--; l>0; optptr++, l--) {
if (*optptr != IPOPT_END) {
*optptr = IPOPT_END;
opt->is_changed = 1;
}
}
goto eol;
case IPOPT_NOOP:
l--;
optptr++;
continue;
}
optlen = optptr[1];
if (optlen<2 || optlen>l) {
pp_ptr = optptr;
goto error;
}
switch (*optptr) {
case IPOPT_SSRR:
case IPOPT_LSRR:
if (optlen < 3) {
pp_ptr = optptr + 1;
goto error;
}
if (optptr[2] < 4) {
pp_ptr = optptr + 2;
goto error;
}
/* NB: cf RFC-1812 5.2.4.1 */
if (opt->srr) {
pp_ptr = optptr;
goto error;
}
if (!skb) {
if (optptr[2] != 4 || optlen < 7 || ((optlen-3) & 3)) {
pp_ptr = optptr + 1;
goto error;
}
memcpy(&opt->faddr, &optptr[3], 4);
if (optlen > 7)
memmove(&optptr[3], &optptr[7], optlen-7);
}
opt->is_strictroute = (optptr[0] == IPOPT_SSRR);
opt->srr = optptr - iph;
break;
case IPOPT_RR:
if (opt->rr) {
pp_ptr = optptr;
goto error;
}
if (optlen < 3) {
pp_ptr = optptr + 1;
goto error;
}
if (optptr[2] < 4) {
pp_ptr = optptr + 2;
goto error;
}
if (optptr[2] <= optlen) {
if (optptr[2]+3 > optlen) {
pp_ptr = optptr + 2;
goto error;
}
if (rt) {
memcpy(&optptr[optptr[2]-1], &rt->rt_spec_dst, 4);
opt->is_changed = 1;
}
optptr[2] += 4;
opt->rr_needaddr = 1;
}
opt->rr = optptr - iph;
break;
case IPOPT_TIMESTAMP:
if (opt->ts) {
pp_ptr = optptr;
goto error;
}
if (optlen < 4) {
pp_ptr = optptr + 1;
goto error;
}
if (optptr[2] < 5) {
pp_ptr = optptr + 2;
goto error;
}
if (optptr[2] <= optlen) {
__be32 *timeptr = NULL;
if (optptr[2]+3 > optptr[1]) {
pp_ptr = optptr + 2;
goto error;
}
switch (optptr[3]&0xF) {
case IPOPT_TS_TSONLY:
opt->ts = optptr - iph;
if (skb)
timeptr = (__be32*)&optptr[optptr[2]-1];
opt->ts_needtime = 1;
optptr[2] += 4;
break;
case IPOPT_TS_TSANDADDR:
if (optptr[2]+7 > optptr[1]) {
pp_ptr = optptr + 2;
goto error;
}
opt->ts = optptr - iph;
if (rt) {
memcpy(&optptr[optptr[2]-1], &rt->rt_spec_dst, 4);
timeptr = (__be32*)&optptr[optptr[2]+3];
}
opt->ts_needaddr = 1;
opt->ts_needtime = 1;
optptr[2] += 8;
break;
case IPOPT_TS_PRESPEC:
if (optptr[2]+7 > optptr[1]) {
pp_ptr = optptr + 2;
goto error;
}
opt->ts = optptr - iph;
{
__be32 addr;
memcpy(&addr, &optptr[optptr[2]-1], 4);
if (inet_addr_type(net, addr) == RTN_UNICAST)
break;
if (skb)
timeptr = (__be32*)&optptr[optptr[2]+3];
}
opt->ts_needtime = 1;
optptr[2] += 8;
break;
default:
if (!skb && !capable(CAP_NET_RAW)) {
pp_ptr = optptr + 3;
goto error;
}
break;
}
if (timeptr) {
struct timespec tv;
__be32 midtime;
getnstimeofday(&tv);
midtime = htonl((tv.tv_sec % 86400) * MSEC_PER_SEC + tv.tv_nsec / NSEC_PER_MSEC);
memcpy(timeptr, &midtime, sizeof(__be32));
opt->is_changed = 1;
}
} else {
unsigned overflow = optptr[3]>>4;
if (overflow == 15) {
pp_ptr = optptr + 3;
goto error;
}
opt->ts = optptr - iph;
if (skb) {
optptr[3] = (optptr[3]&0xF)|((overflow+1)<<4);
opt->is_changed = 1;
}
}
break;
case IPOPT_RA:
if (optlen < 4) {
pp_ptr = optptr + 1;
goto error;
}
if (optptr[2] == 0 && optptr[3] == 0)
opt->router_alert = optptr - iph;
break;
case IPOPT_CIPSO:
if ((!skb && !capable(CAP_NET_RAW)) || opt->cipso) {
pp_ptr = optptr;
goto error;
}
opt->cipso = optptr - iph;
if (cipso_v4_validate(skb, &optptr)) {
pp_ptr = optptr;
goto error;
}
break;
case IPOPT_SEC:
case IPOPT_SID:
default:
if (!skb && !capable(CAP_NET_RAW)) {
pp_ptr = optptr;
goto error;
}
break;
}
l -= optlen;
optptr += optlen;
}
eol:
if (!pp_ptr)
return 0;
error:
if (skb) {
icmp_send(skb, ICMP_PARAMETERPROB, 0, htonl((pp_ptr-iph)<<24));
}
return -EINVAL;
}
EXPORT_SYMBOL(ip_options_compile);
/*
* Undo all the changes done by ip_options_compile().
*/
void ip_options_undo(struct ip_options * opt)
{
if (opt->srr) {
unsigned char * optptr = opt->__data+opt->srr-sizeof(struct iphdr);
memmove(optptr+7, optptr+3, optptr[1]-7);
memcpy(optptr+3, &opt->faddr, 4);
}
if (opt->rr_needaddr) {
unsigned char * optptr = opt->__data+opt->rr-sizeof(struct iphdr);
optptr[2] -= 4;
memset(&optptr[optptr[2]-1], 0, 4);
}
if (opt->ts) {
unsigned char * optptr = opt->__data+opt->ts-sizeof(struct iphdr);
if (opt->ts_needtime) {
optptr[2] -= 4;
memset(&optptr[optptr[2]-1], 0, 4);
if ((optptr[3]&0xF) == IPOPT_TS_PRESPEC)
optptr[2] -= 4;
}
if (opt->ts_needaddr) {
optptr[2] -= 4;
memset(&optptr[optptr[2]-1], 0, 4);
}
}
}
static struct ip_options_rcu *ip_options_get_alloc(const int optlen)
{
return kzalloc(sizeof(struct ip_options_rcu) + ((optlen + 3) & ~3),
GFP_KERNEL);
}
static int ip_options_get_finish(struct net *net, struct ip_options_rcu **optp,
struct ip_options_rcu *opt, int optlen)
{
while (optlen & 3)
opt->opt.__data[optlen++] = IPOPT_END;
opt->opt.optlen = optlen;
if (optlen && ip_options_compile(net, &opt->opt, NULL)) {
kfree(opt);
return -EINVAL;
}
kfree(*optp);
*optp = opt;
return 0;
}
int ip_options_get_from_user(struct net *net, struct ip_options_rcu **optp,
unsigned char __user *data, int optlen)
{
struct ip_options_rcu *opt = ip_options_get_alloc(optlen);
if (!opt)
return -ENOMEM;
if (optlen && copy_from_user(opt->opt.__data, data, optlen)) {
kfree(opt);
return -EFAULT;
}
return ip_options_get_finish(net, optp, opt, optlen);
}
int ip_options_get(struct net *net, struct ip_options_rcu **optp,
unsigned char *data, int optlen)
{
struct ip_options_rcu *opt = ip_options_get_alloc(optlen);
if (!opt)
return -ENOMEM;
if (optlen)
memcpy(opt->opt.__data, data, optlen);
return ip_options_get_finish(net, optp, opt, optlen);
}
void ip_forward_options(struct sk_buff *skb)
{
struct ip_options * opt = &(IPCB(skb)->opt);
unsigned char * optptr;
struct rtable *rt = skb_rtable(skb);
unsigned char *raw = skb_network_header(skb);
if (opt->rr_needaddr) {
optptr = (unsigned char *)raw + opt->rr;
ip_rt_get_source(&optptr[optptr[2]-5], rt);
opt->is_changed = 1;
}
if (opt->srr_is_hit) {
int srrptr, srrspace;
optptr = raw + opt->srr;
for ( srrptr=optptr[2], srrspace = optptr[1];
srrptr <= srrspace;
srrptr += 4
) {
if (srrptr + 3 > srrspace)
break;
if (memcmp(&rt->rt_dst, &optptr[srrptr-1], 4) == 0)
break;
}
if (srrptr + 3 <= srrspace) {
opt->is_changed = 1;
ip_rt_get_source(&optptr[srrptr-1], rt);
optptr[2] = srrptr+4;
} else if (net_ratelimit())
printk(KERN_CRIT "ip_forward(): Argh! Destination lost!\n");
if (opt->ts_needaddr) {
optptr = raw + opt->ts;
ip_rt_get_source(&optptr[optptr[2]-9], rt);
opt->is_changed = 1;
}
}
if (opt->is_changed) {
opt->is_changed = 0;
ip_send_check(ip_hdr(skb));
}
}
int ip_options_rcv_srr(struct sk_buff *skb)
{
struct ip_options *opt = &(IPCB(skb)->opt);
int srrspace, srrptr;
__be32 nexthop;
struct iphdr *iph = ip_hdr(skb);
unsigned char *optptr = skb_network_header(skb) + opt->srr;
struct rtable *rt = skb_rtable(skb);
struct rtable *rt2;
unsigned long orefdst;
int err;
if (!rt)
return 0;
if (skb->pkt_type != PACKET_HOST)
return -EINVAL;
if (rt->rt_type == RTN_UNICAST) {
if (!opt->is_strictroute)
return 0;
icmp_send(skb, ICMP_PARAMETERPROB, 0, htonl(16<<24));
return -EINVAL;
}
if (rt->rt_type != RTN_LOCAL)
return -EINVAL;
for (srrptr=optptr[2], srrspace = optptr[1]; srrptr <= srrspace; srrptr += 4) {
if (srrptr + 3 > srrspace) {
icmp_send(skb, ICMP_PARAMETERPROB, 0, htonl((opt->srr+2)<<24));
return -EINVAL;
}
memcpy(&nexthop, &optptr[srrptr-1], 4);
orefdst = skb->_skb_refdst;
skb_dst_set(skb, NULL);
err = ip_route_input(skb, nexthop, iph->saddr, iph->tos, skb->dev);
rt2 = skb_rtable(skb);
if (err || (rt2->rt_type != RTN_UNICAST && rt2->rt_type != RTN_LOCAL)) {
skb_dst_drop(skb);
skb->_skb_refdst = orefdst;
return -EINVAL;
}
refdst_drop(orefdst);
if (rt2->rt_type != RTN_LOCAL)
break;
/* Superfast 8) loopback forward */
iph->daddr = nexthop;
opt->is_changed = 1;
}
if (srrptr <= srrspace) {
opt->srr_is_hit = 1;
opt->is_changed = 1;
}
return 0;
}
EXPORT_SYMBOL(ip_options_rcv_srr);
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